The present invention relates to continuous air flow overlays or mattresses that are disposed between a patient and a rigid support and more particularly to those that regulate the pressure.
U.S. Pat. No. 4,896,389 to Chamberland, which is assigned to a company related to the assignee of this application, discloses an inflatable air mattress in the form of an overlay that is used to improve the comfort of patients that are immobilized over long periods of time, and is hereby incorporated herein by this reference. A compressor supplies this mattress overlay with a continuous flow of air. The pressure supplied by the compressor is adjusted manually to suit the comfort of the individual patient. As the patient changes his or her body position on the overlay, an additional manual adjustment of the compressor pressure can be made to suit the comfort of the patient in the new position.
In U.S. Pat. No. 4,488,322 to Hunt et al, a mattress body incorporates a plurality of header chambers 19 which are connected to air supply conduits 11, 13. Air is supplied from a blower which contains pressure control valves for each supply conduit. One end of each of a plurality of inflatable sacs 10 is connected to a connector 21 in a header chamber 19 so that air can be supplied to the air sac 10 via the conduits 11, 13 and header chamber 19. The other end of each of the plurality of inflatable sacs 10 is connected to a connector 22 in an exhaust header chamber 20, which is connected to an exhaust conduit 23. A flow control valve 31 is linked between the corresponding exhaust conduit 23 and supply conduit 11 to eliminate small differences in air flow through each group of air sacs.